1. Field of the Invention
This invention relates to a process for preparing .DELTA..sup.11 steroid compounds from corresponding 12-hydroxy steroids. In a particular aspect, this invention relates to the introduction of .DELTA..sup.11 unsaturation into steroid compounds which are also substituted in the C-7 position. The process of this invention is particularly useful in the preparation of chenodeoxycholic acid from cholic acid.
2. Description of the Prior Art
Chenodeoxycholic acid has been found to be quite useful in the medical field and particularly in the treatment of gallstones. The major source of this acid is by synthesis from cholic acid. The prior art processes for this synthesis, however, involve complicated reaction sequences characterized by low yield and high cost. Due to the increased importance of chenodeoxycholic acid in the medical field and the quantities that are needed there exists a great need for an efficient, inexpensive process for its manufacture.
The production of chenodeoxycholic acid (CDC) from cholic acid involves the removal of the C-12 hydroxy group from the cholic acid without removing the C-7 hydroxy group. It is in this aspect that prior art processes for obtaining .DELTA..sup.11 unsaturation are unsatisfactory in the production of CDC. One such prior art process is described in U.S. Pat. No. 3,325,483 to Bharucha et al. In this process a 12-sulfonate steroid is dehydrosulfonated by treating with metal glycolates or salts of alkoxypolyethylene glycols to provide .DELTA..sup.11 unsaturation. However, in the synthesis of CDC, this process removes a large proportion of the C-7 substituent even when the substituent is blocked and the major product obtained is the 6,11-dienate. Thus only a small yield of the desired CDC is achieved. In U.S. Pat. No. 3,164,616 Bharucha describes a similar process wherein a strong metallic alkoxide base is used to treat the 12-sulfonate. However, this process yields only the unwanted 6,11-dienate and no 11-enate is formed.
There remains a great need for a high yield, inexpensive process for forming CDC to fill the necessary need for the materials for medical uses.